It is common practice to construct outboard motors such that they have forward and reverse gears located in a gear case below the water line and with the gears being mounted on the propeller shaft. An example of such a construction is shown in the Holtermann U.S. Pat. No. 3,817,202. In outboard motors having such a construction, shifting is accomplished by moving a clutch dog which comprises a spool that is splined to the propeller shaft and which has opposed faces selectively engageable with either the forward or reverse driven gears, the clutch dog being splined on the propeller shaft and being axially movable thereon between a position between the forward and reverse gears to alternative positions engaging those gears and thus driving the propeller shaft in the desired direction.
One of the potential problems of a construction as defined above is that the axially slidable clutch dog may be subjected to excessive stress and wear since the clutch dog is trying to center itself on two surfaces disposed at an angle of 90.degree., one of those surfaces being the spline on the propeller shaft and the other of those surfaces being the driving lugs on the forward or reverse driven gear.
Another potential disadvantage of the prior art construction lies in the required shape of the gear case. It is desired to make the gear case as small as possible in order to reduce the fluid drag on the outboard motor, and it is also desired to construct a gear case with a pointed parabolic shape. When the gear case must accommodate two gears, i.e. the forward and reverse driven gears on the propeller shaft as well as a shiftable clutch dog, the leading end of the gear case tends to become bulbous rather than the desired parabolic shape.
Examples of prior art transmissions are illustrated in the Cole U.S. Pat. No. 1,241,924; the Deves U.S. Pat. No. 1,093,920; the Anderson U.S. Pat. No. 1,390,262; and the Roeder U.S. Pat. No. 1,979,080.
Attention is also directed to the Baer et al. U.S. Pat. No. 2,042,577; the Kries U.S. Pat. No. 2,086,809; the Semery U.S. Pat. No. 2,110,180; the Baumgartner U.S. Pat. No. 2,165,201; and the Kriedler U.S. Pat. No. 2,861,461.